My characters are too weak to do any good stuff, so I'm asking for help on a place to train. I'd rather not have monsters that can hit in excess of a few hundred - most of those characters have just over 1000HP, and Rydia has less.

do the sylvan and lands of summon side quest so you can level up much faster tip: have rosa use float on all floors in both dungeons and there is a monster in the land of summons known as the "summoner" look for the one that casts arachne instead of king naga ... arachne uses earthquake most of the times and since you are on float it doesn't affect you and you just kill it and wait for the summoner to once again summon it ... in this way you can get in instant battles that can't harm you and the summoner rarely attacks so your hp stays the same if it decreases just let rosa use "pray" for free healing ... just wait for the summoner to summon another one ... note : things you can steal a healing rod from summoner , eyedrop : king naga , spider silk : arachne .... hope this helps!